O.K., it is not claimed that Columbus was a Muslim, but there is a widespread claim in Muslim circles that he relied on an Arab book and Muslim navigators to discover the Americas, for which there is no evidence really. It is also a widespread claim that Muslim ships discovered the Americas centuries before Columbus, also without evidence.
–
Eugene SeidelOct 15 '13 at 15:45

1

I suggest you qualify a bit what you mean by conversion: If someone acts publicly as a Muslim but in private remains an observant Jew (not so difficult to do) is that called conversion? Does coerced conversion count?
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user2590Oct 16 '13 at 9:14

2

Suggest that you remove the word famous and rephrase the question. "Who is the most authoritative Rabbi to convert to Islam?" "Famous" is distracting the discussion from what seems to be your core question.
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Mark C. WallaceOct 16 '13 at 20:00

1

@Coelacanth - I was under impression that conversion to Islam has some well defined rules and formal process?
–
DVKOct 16 '13 at 20:53

1

@DVK - I really don't know. But I'm not sure that's relevant if you're just "going through the motions" because you're forced, but don't mean it.
–
user2590Oct 16 '13 at 23:30

2 Answers
2

Abdullah Bin Salam: He is the first Jewish Rabbi to convert to Islam. Before conversion he was called as Husayn bun Salam. The conversion happened at the time of Muhammad himself.
Following narrative about his conversion is reported in the collection of authentic historical traditions of Islam:

Prophet Muhammad asks the Jewish community:

“What is the status of Al-Husayn ibn Salam among you?”

“He is our sayyid (leader) and the son of our sayyid. He is our rabbi
and our alim (scholar), the son of our rabbi and alim.”

“If you come to know that he has accepted Islam, would you accept
Islam also?” asked the Prophet.

“God forbid! He would not accept Islam. May God protect him from
accepting Islam,” they said, horrified.

At this point I came out in full view of them and announced: “O
assembly of Jews! Be conscious of God and accept what Muhammad has
brought. By God, you certainly know that he is the Messenger of God
and you can find prophecies about him and mention of his name and
characteristics in your Torah. I for my part declare that he is the
Messenger of God. I have faith in him and believe that he is true. I
know him.”

Sabatai Zevi : Was a very famous Rabbi of his time , to the extent many of the Jews started believing him as the Messiah and he claimed it too. Some people claim that he was coerced , this might be true but later in life he truly accepted Islam and also bought 300 Jewish families to Islam:

Sarah and approximately 300 families among Sabbatai's followers also
converted to Islam. These new Muslims thereafter were known as dönmeh
(converts).3 The sultan's officials ordered Sabbatai to take an
additional wife to demonstrate his conversion. Some days after his
conversion he wrote to Smyrna: "God has made me an Ishmaelite; He
commanded, and it was done. The ninth day of my
regeneration."

Maimonides - (RAMBAM) : Many historical sources seem to support the idea that RAMBAM may have been coerced into converting to Islam, although this is highly debatable:

A Muslim historian, Ibn al-Qifti (1172-1248) reports nothing less than
that the Rambam himself, on numerous occasions, voluntarily went to
mosques to pray 1, under no compulsion and seeing no contradiction
with his Judaism. Ibn al-Qifti notes that this was towards the end of
Maimonides’ life and was not an event of his youth, under fear of the
Al-Mohades who had invaded Al-Andalus in his youth.1

Kenneth Seeskin
writes, in The Cambridge Companion to Maimonides, “although Ibn
al-Qifti’s book has come down to us in a later recension, and contains
some errors, we have no reason to doubt the information on
Maimonides.”2

After the recovery of Toledo from the Moors by the Crusaders in 1085,
European scholars flocked there to translate the ancient classical
texts from the Greek (which Europe had forgotten) to Arabic and Hebrew
and Latin, making it the first part of the European Middle Ages
(1100-1543), the names of some European scholars appeared in
scientific literature next to a large number of Muslim scholars,
including Ibn Rushd (Averroes), Maimouna Ibn Moussa (Maimonides),
Tousi and Ibn Nafis.

Another point of view regarding Rambam can be that he practiced both Judaism and Islam simultaneously, In Jewish Encyclopedia , we find the fact that , belief in Muhammad pbuh is not equatable to Idolatry and hence wont demand sacrifice of life as is the case of the law for Idolatry, thus making Islam simply as a sect within Judaism:

Rabbi M. Friedländer in ("Guide of the Perplexed," i., xvii., xxxiii.,
et seq.), in which Islam is declared to be simply a belief in
Mohammed, and that Islam is not idolatry, to avoid which only the Law
demands the sacrifice of life.

Hence it is halachically possible for a Jew to become a Muslim , A Jew wont loose his Jewishness by accepting Islam. Rambam realized this very well as quoted above in his most popular work. hence it is fair seeming that he purposely did not show any resistance to Dawah on him and accepted Islam. His acceptance of Islam may not be genuine but he was a very ambitious and rational intellectual whose conversion was a pragmatic decision which would help him gain acceptance and position of influence from the Sultans of the time as reported by Al-Baghdadi in Seeskin:

he was of superior merit, but love of authority and serving powerful
people prevailed over him

was too much concerned with worldly successand frequenting the great
as their physician

Kraemer also found sources that indicate that while in Fustat (old
Cairo), the Rambam was confronted by a man named Abu ‘l-’Arab ibn
Mu’isha, a jurist from Andalusia, who recognized that the leader of
the Jewish community in Egypt was no longer practicing Islam (a crime
punishable by death under Islamic law). The Rambam managed to escape
persecution although the historical records give conflicting reports
as to how that happened.

In this work (Ifham Yahud) he points out that from time to time the
abrogation of the Law is necessary and that, in fact, it has often
occurred in Judaism. He tries to prove the prophetic character of
Jesus and of Mohammed; claiming that the first of these is referred to
in Gen. xlix. 10, and the latter in Gen. xvii. 2 ( has numerically the
same value as Mohammed). He affirms that the Jews of his time possess
the Torah of Ezra and not that of Moses, and that too many laws have
been added by the sages of the Mishnah and the Gemara.

Samuel makes the curious statement in ("Monatsschrift," xlii. 260) :

that most of the Karaites had gone over to Islam, because their system
is free from all the absurdities of the Rabbinites, and their theology
not so different from that of the Mohammedans.

Yosef Cohen A former rabbi belonging to the Satmar Hasidic community in Brooklyn.

Several comments were marked as obsolete. Given that this answer is completely unlike its original form, I didn't really have the patience to wade through all 26 to figure out which were still relevant, so I've purged them all. Everyone gets a do-over.
–
T.E.D.♦Oct 20 '13 at 14:16

3

-1 : This answer has become a mish-mosh of inconsistencies, irrelevancies, and bad sources, with a seeming agenda to prove that RAMBAM converted to Islam, although there is no credible evidence whatsoever cited for this. (And what RAMBAM's grandson did or did not do has no bearing whatsoever on the question.) This answer needs a complete makeover.
–
user2590Oct 22 '13 at 17:03

3

This answer seems quite desperate. Claiming that Joseph Cohen is an example. For those that don't know.. Joseph Cohen or Joseph Kaplan, was never a rabbi, he was a Jew that was secular, became religious (black hat), then became muslim spoke of how he'd love his sons to be martyrs killing jews, and was investigated by the FBI after a bomb threat against a Jewish organization. He is a fundamentalist muslim now(has been since around 2000), but was never a rabbi. And the question asked for notable rabbis.
–
barlopFeb 9 '14 at 1:10

4

Maimonides(who you call a Muslim) in his Laws of concerning the coming of messiah, referred to Mohammed as a mad man.. and was very critical of muslims in his letter to yemen, and a letter published in english by andrew bostom. And in one letter he said it's OK to teach torah to christians but not to muslims because they do not accept the text and would pervert what they are taught. And if I recall he had great praise for a convert to judaism from islam, for that man making that transition against the man's own family, but for the sake of truth.
–
barlopFeb 9 '14 at 1:14

1

Your first example is "sourced" in Islamic tradition, which doesn't mean anything without support. Having a story saying "one of them converted to us" doesn't mean anything without independent verification. Your second example isn't sourced at all (w.r.t. it being sincere). Your claims about the Rambam have been covered by other comments already.
–
Monica CellioJul 14 '14 at 21:37

-1 - Sabbatai Zevi was in no way, shape or form a "famous rabbi". He was trained as a rabbi, but he was famous for being a claimed messiah, NOT for his rabbinical knowledge.
–
DVKOct 16 '13 at 13:08

2

@Ali - leaving aside the accuracy of your example, Zevi was the opposote - he was NOT popular as a famous Rabbi. He was popular as wannabe Messiah (and NOT a noted Rabbinical scholar/sage).
–
DVKOct 16 '13 at 14:59

@Felix Goldberg: Whatever you wish - you asked for a famous rabbi. You may have fallen into DVK and Coelacanth's "no true Scotsman" trap. In fact his claims to authority not restricted to a small group, but instead divided Jewish communities with most synagogues praying for him, and were for example endorsed by the Chief Rabbi of Amsterdam.
–
HenryOct 16 '13 at 20:15

3

@Henry - there's a difference between being famous and famous for X. Paris Hilton is famous. And she's a movie actress. But she's NOT in any way, shape or form famous as a movie actress. Zevi had followers NOT because he was a big-time famous rabbi, but simply because he claimed to be a Messiah. Had he not made that claim, he'd have been a little-known rabbi from somewhere, known to his congregarion and may be some neighbours. Can you produce a single notable work of Rabbinical/Talmudic scholarship that he produced separately from his Messianic claims?
–
DVKOct 16 '13 at 20:45